The present invention relates to textile treatment compositions for imparting water/soil resistance to fibrous substrates, including textiles.
Two methods of imparting hydrophobic character to textiles have been investigated in the past: 1) hydrophobic polymer films, and 2) attachment of hydrophobic monomers and polymers via physi- or chemisorptive processes.
Current commercial processes for producing water-repellent/soil-resistant fabrics are mainly based on the laminating processes of companies such as W. L. Gore and Sympatex (Journal of Coated Fabrics vol. 26, 1996, pp. 107-130) and polysiloxane coatings (Handbook of Fiber Science and Technology, Marcel Dekker, New York, N.Y., Vol. II, 1984, pp. 168-171). The laminating process involves adhering a layer of polymeric material (such as Teflon(trademark) that has been stretched to produce micropores) to a fabric. Although this process produces durable repellent films, it suffers from many disadvantages. The application of these laminants requires special equipment and therefore cannot be applied using existing textile production processes. Synthesis of the film is costly and garments with this modification are significantly more expensive than their unmodified counterparts. The colors and shades of this clothing are limited by the coating color. Finally, clothing made from this material tends to be heavy and stiff. Polysiloxane films suffer from low durability to laundering, which tends to swell the fabric and rupture the silicone film. The polysiloxanes have a cost advantage over the laminates, which are, however, more durable to laundering and dry-cleaning.
Repellents based on monomeric hydrocarbon hydrophobes can be broken down into five categories: 1) aluminum and zirconium soaps, 2) waxes and waxlike substances, 3) metal complexes, 4) pyridinium compounds, 5) methylol compounds, and 6) other fiber-reactive water repellents. Compared to polymeric coatings, monomeric hydrophobes can penetrate within the fabric to produce a more durable coating.
One of the oldest water repellents was based on non-covalently applying water-soluble soap to the fibers and precipitating it with an aluminum salt (J. Text. Res. vol. 42, 1961, p. 691). These coatings dissolved in alkaline detergent solution, therefore washfastness was poor. Zirconium soaps were less soluble in detergent solutions (Waterproofing and Water-Repellency, Elsevier Publ. Co., Amsterdam, 1963, p. 188), but due to the noncovalent nature of attachment to the fabric, abrasion resistance was poor.
The oldest and most economical way to make fabric water repellent is to coat it with a hydrophobic substance, such as paraffin (Text Inst. Ind. vol. 4, 1966, p. 255). This process is still in practice today and paraffin emulsions for coating fabrics can be purchased (e.g., Freepel(copyright)) from BFGoodrich Textile Chemicals, Inc.). Waxes are not stable to laundering or dry cleaning. Durability is poor due to their noncovalent nature of binding and their breathability is low.
Quilon chrome complexes polymerize to form xe2x80x94Crxe2x80x94Oxe2x80x94Crxe2x80x94 linkages (Tappi vol. 36, 1953, p. 107). Simultaneously, the complex forms covalent bonds with the surface of fibers with hydrophobic chains directed away from the surface to produce a water repellent, semi-durable coating. Quilon solutions require acidic conditions to react, thus causing degradation of the cellulose fibers through cellulose hydrolysis. Fabric colors are limited by the blue-green coloration imparted by the metal complex.
The extensive history of pyridinium-type water repellents has been reviewed by Harding (J. Text. Res. vol. 42, 1951, p. 691). In essence, an alkyl quaternary ammonium compound is reacted with cellulose at elevated temperatures to form a durable water-repellent finish on cotton (Br. Pat. 466,817) and a later version was marketed under the trademark Velan PF by ICI. It was later found that the reaction was restricted to the surface of the fibers (J. Soc. Dyers Colour. vol. 63, 1947, p. 260) and the high cure temperature weakened the fabric. Sodium acetate had to be added to prevent the decomposition of the cellulose by the HCl formed. Also, the pyridine liberated during the reaction has an unpleasant odor and the fabric had to be scoured after the cure. The toxicological properties of pyridine ended its use in the 1970 s when government regulations on such substances increased.
Methylol chemistry has been extensively commercialized in the crosslinking of cellulose for durable press fabrics. N-methylol compounds are prepared by reaction of an amine or amide with formaldehyde. Alkyl-N-methylol compounds can be reacted at elevated temperatures in the presence of an acidic catalyst with the hydroxyl groups of textiles to impart durable hydrophobic qualities (Br. Pats. 463,300 and 679,811). The reaction is accompanied by formation of non-covalently linked (i.e., non-durable) resinous material, thus decreasing efficiency. In addition, the high temperature and acid catalyst reduce the strength of the fabric. Recently, the commercial use of methylol compounds has been waning due to concerns of toxic formaldehyde release from fabrics treated in such a manner.
Several other chemical reactions have been used to covalently attach hydrophobic species to cotton to produce a water-repellent finish but have not been commercialized for various reasons. Long-chain isocyanates have been used in this respect (Br. Pat. 461,179; Am. Dyest. Rep. vol. 43, 1954, p. 453; Br. Pat. 474,403). The high toxicity of isocyanates and significant side reactions with water, however, precluded it from commercial use. To circumvent the water sensitivity of isocyanates, alkyl isocyanates were reacted with ethylenimine to yield the less reactive aziridinyl compound, which was subsequently reacted with cellulose at 150xc2x0 C. (Ger. Pat. 731,667; Br. Pat. 795,380). Although the toxicity of the aziridinyl compound was reduced compared to the isocyanate, the procedure still required the handling of toxic isocyanate precursors. Also, the high cure temperature weakened the cellulose, and crosslinkers were needed to increase structural stability. Alkyl epoxides can be reacted with cellulose under acidic or basic conditions to produce durable, water-repellent cotton (Ger. Pat. 874,289). The epoxide was applied from a volatile solvent to suppress side reactions with water. Epoxides are, in general, not very reactive, thus requiring long reaction times at high temperatures. Therefore, they have not been commercialized. Acylation of cotton with isopropenyl stearate from an acidic solution of benzene and curing at 200xc2x0 C. produced a durable hydrophobic coating (U.S. Pat. No. 4,152,115). The high cure temperature and acid catalyst again weakened the cotton. Carcinogenic benzene can be replaced by toluene, but the practicality of using flammable solvents in fabric finishing is limited. Alkyl vinyl sulfones react with cellulose in the presence of alkali to form a repellent finish (U.S. Pat. No. 2,670,265). However, this method has not been commercialized because the alkali is not compatible with cross-linking reactants required for permanent press treatments.
Recently, copolymers containing a fluorinated monomer, an alkyl monomer, a reactive monomer (e.g., hydroxyethylmethacrylate, N-methylol acrylamide), and various other auxiliary monomers (e.g. vinylidene chloride, polyethylene glycol methacrylate, etc.) have become popular commercial products for the aqueous application of somewhat durable water and oil repellent finish to textiles (e.g., Zonyl(trademark) by DuPont, Nuva(trademark) by Clariant, and Scotchgard(trademark) by 3M). These polymers, however, suffer from the release of formaldehyde from the treated fabric due to the breakdown of the N-methlyol acrylamide portion of the copolymer.
The use of mordants (insoluble metal complexes) have been used to permanently attach fluorinated compounds (containing groups such as acids capable of forming insoluble complexes with the mordant metal) to a textile substrate. The mordant approach of attaching the fluorinated compound to the substrate eliminates the use of the formaldehyde-releasing components described above. U.S. Pat. No. 3,651,105 uses a solvent-soluble fluorinated metal complex that is applied to paper and fabric. This complex is monomeric, so it only has one point of attachment as opposed to multiple attachment points afforded by a polymer. But, more importantly, this complex is only soluble in a carbon tetrachloride/isopropanol mixture. The use of toxic and flammable solvents in a textile process is impractical. Water-soluble complexes are preferred. U.S. Pat. No. 3,467,612 uses a water-soluble fluoropolymer/metal complex but the fluoropolymer does not contain any monomers capable of complexing with a divalent metal to bridge to a substrate. However, although the fluorinated complex is insolubilized on the fabric, it is not directly bound to a group on the substrate; thus durability to abrasion is low. Other patents using divalent metals use a two-step process where the metal is applied to the fabric first and then the fluoropolymer containing a monomer capable of complexing a divalent metal is applied to the fabric in a second step. EP 0710738 teaches a two-step process: application of a divalent metal followed by application of a random fluoro-copolymer (containing monomers capable of binding the divalent metal). The use of two steps greatly decreases the utility of this approach due to cost issues. U.S. Pat. No. 5,744201 uses a water-soluble random fluoro-copolymer with an acid-containing monomer that is rendered insoluble (and thus precipitated on the fabric) by changing the pH in the presence of ammonium ion (single valent). The copolymer and the ammonium ion form an insoluble complex at a specific pH and is not directly bound to a group on the substrate; thus durability to abrasion is low. EP 572269A1 is similar except for the use a polyallylamine salt instead of ammonium. This patent also mentions the use of monomeric fluorinated zirconium compounds as additives to boost performance. U.S. Pat. No. 4,695,488 incorporates acrylic acid in their fluoropolymer to increase soil release properties but do not use this acid group to form insoluble divalent salt linkages to the fabric substrate. The purpose of the acid groups is to increase the soil-release properties of the finish.
This invention is directed to treatment preparations useful for the treatment of fibrous substrates, such as textiles and other webs, to provide substantially permanent, durable water and soil repellency to keratinous and/or cellulosic fibrous substrates. More particularly, the invention is directed to preparations that comprise a fluorinated polymer and metal atoms, typically as a metal salt. The claimed fluorinated copolymer incorporates the divalent metal salt but is still water-soluble (because of water-soluble monomers in the polymer and surfactants), allowing for a one-step application of both the fluoropolymer and metal. The divalent metal will complex with groups on the fabric to make an insoluble complex on the fabric that is directly bound to the substrate of the fabric for increased abrasion durability. Furthermore, the claimed fluorinated copolymer is a block copolymer in which the polymer has long stretches of only fluoromonomer and long stretches of monomers capable of complexing divalent metals. This increases the water solubility of the polymer of the present invention and increases the strength with which the polymer binds to the fiber through a divalent metal.
In a first embodiment, the preparations of the invention comprise (a) a fluorinated carboxylate-functionalized fluoropolymer and (b) a metal salt, or mordant.
In a second embodiment, this invention comprises a solution, emulsion or suspension of (a) a fluorinated polymer that contains functional moieties or reactive groups that can complex with metal atoms that have a formal charge of 2 or greater, and (b) one or more metal atoms that have a formal charge of 2 or greater.
By xe2x80x9cfluorinated polymerxe2x80x9d or xe2x80x9cfluoropolymerxe2x80x9d is meant that the polymer will contain some perfluorinated or partially fluorinated alkyl chains to impart water and oil repellency to coated objects. It may additionally be advantageous for the polymer to contain other groups such as normal alkyl chains; groups that can increase the water solubility or stability of the suspension of the polymer, such as chains of polyethylene glycol or other polar groups; one or more different groups that can crosslink to each other or to the material being coated; or groups that increase polymer flexibility, flame retardancy, the softness of a textile, or resistance to bacteria or mildew.
The metal atoms in the solution of the second embodiment can come from two sources. Either they are part of a monomer that is copolymerized to become part of the polymer, such as calcium, magnesium, aluminum, or chromium acrylate; or they are added in the form of a compound that has a metal with a formal charge of 2 or greater. This addition of the metal can take place before polymerization, during polymerization, or after polymerization. Without being bound by theory, it is believed that the metal atoms may complex with keratinous or any other fibrous substrates that contain free carboxyl groups. By xe2x80x9ccomplexingxe2x80x9d is meant that the polymer will form a coordination bond with the metal and the metal will form a coordination bond to the fiber, textile, or web to be treated. Alternatively, again without being bound by theory, the metal atoms may act to crosslink the polymer to itself and to other chains to make the polymer insoluble in the fibrous substrate. In either case, the resulting water/soil repellent preparation has more durable water and soil repellency in and/or on the substrate fiber structure while retaining the natural properties of the fibrous substrate.
This invention is further directed to a novel block copolymer containing i) one or more blocks composed primarily of acrylic acid, methacrylic acid, maleic anhydride, maleic acid, crotonic acid, itaconic acid, or other acid-containing monomers, and ii) one or more blocks that contain a significant amount of a fluorinated monomer that is capable of binding to wool or other fibrous substrates with a metal. They may further comprise a monomer that contains a metal, such as calcium, magnesium, aluminum, potassium, or chromium acrylates or styrene sulfonates.
This invention is further directed to the yarns, fibers, fabrics, textiles, webs, finished goods, or nonwovens (encompassed herein under the terms xe2x80x9ctextilesxe2x80x9d and xe2x80x9cfibrous substratesxe2x80x9d) treated with the water- and soil-resistant preparations of the invention. Such fibrous substrates exhibit a greatly improved, durable water and soil repellency. By xe2x80x9cdurable water and soil repellencyxe2x80x9d is meant that the fibrous substrate will exhibit a repellency or resistance to water and oily soils even after multiple launderings.
Methods are provided for treating fabrics and other fibrous substrates with permanent water/soil repellent coatings.